High power density inverter (II)

ABSTRACT

The present invention relates to a single phase, non-insulated, miniaturized DC/AC power inverter having an output power density higher than 3000 W/dm3, wherein said power inverter is packaged in a casing made of an external electrically conductive enclosure containing a fan blowing in an axial direction to a side face of the casing and, in a stacked elevation arrangement, successively from a bottom side to a top side, a layer of active filter capacitors, a heatsink, a layer of wideband semiconductors switches connected to a PCB with thermal vias and a layer of active filtering inductors, the fan and the component stacked arrangement being designed so as, in operation, the external temperature of the casing does not overcome 60° C. in any point, for an ambient temperature of maximum 30° C. under a maximum load of 2 kVA.

FIELD OF THE INVENTION

The present invention relates to a single phase, non-insulated,miniaturized DC/AC power inverter having a very high, preferablyextremely high output power density.

TECHNOLOGICAL BACKGROUND AND PRIOR ART

Power inverters (or in short inverters) are electronic devices whichtransform direct current (DC) to alternating current (AC). Inparticular, inverters play nowadays an economic and environmental rolewhich is more and more important in the frame of transformation of DCcurrent produced by solar panels, batteries or similar sources into ACcurrent for domestic or industrial use as well as in electric cars.

Inverters manufactured by the Applicant for commercial and industrialcompanies permit saving of their critical applications by using energystored in batteries, during distribution grid breakdown. Inverter Media™manufactured by the Applicant already allows to reach a power density of680 W/liter at 2 kVA.

Inverters used for example in electricity production facilities fromsolar energy still have a noticeable size (typically 50 liters or thesize of a portable cooler). Size reduction of >10× in volume, i.e.typically shrinking down to something smaller than a small laptop wouldenable powering more homes with solar energy, as well as improvingdistribution efficiency and distances ranges reached with electricalgrids. Future will thus be dedicated to more robust, more reliable andmore intelligent power inverters.

In order to achieve very high power density and consequently smallerconversion systems, designers of inverter topologies had primarily totarget increased efficiency and common mode (CM) noise reduction. Higherefficiency has been achieved thanks to improvements in semiconductormaterials and processing, as well as in magnetic materials. Use ofwideband-gap semiconductors (silicon carbide—SiC or gallium nitride—GaN)allows to improve efficiency in high frequency power converters, whilethe latter allow increasing switching frequency and thus reducingpassive components size.

It is known that EMI noise is both in the form of conducted EMI, i.e.noise travelling along wires or conducting paths and through electroniccomponents and in the form of radiated EMI (RFI), i.e. noise travellingthrough the air in the form of electro-magnetic fields or radio waves.In high-speed switching converters (frequency typically from 50 kHz to 1MHz), most of the conducted EMI comes from the switching transistors andfrom the rectifiers. For preventing such EMI noise, one generally usesEMI filters made of passive components such as capacitors and inductorsforming LC circuits. Conducted EMI is divided into common-mode noise(CMN) and differential-mode noise (DMN). CMN flows in the same directionin line and neutral AC power conductors, is in phase with itselfrelative to ground and returns to ground. Suitable CMN filter comprisesinductors L100, L200 placed in series with each power line andrespective Y-capacitors C100, C200 connecting each power conductors toground (see for example CMN filter 100 in FIG. 1 in the case of a DC/ACconverter). DMN exists between AC line and neutral conductors and is180° out of phase with itself. Suitable DMN filter comprises C340X-capacitors bridging the power lines, possibly supplemented bydifferential-suppression inductors L300, L400 (see for example DMNfilter 101 in FIG. 1 in the case of a DC/AC converter).

AIMS OF THE INVENTION

The present invention aims at providing a power inverter havingextremely high output power density.

In particular the invention is targeting to deliver an inverter havingan output power density greater than 50 W/in³ (or 3051 W/dm³ or W/liter)on a maximum load of 2 kVA.

Another goal of the present invention is to allow use of wideband-gapsemiconductor switches, while assuring soft switching thereof forreducing switch losses, and while keeping inside acceptable limits forEMI noise generated by the very high switching speed of these componentsand while suitably managing high dV/dt in the switch commands.

SUMMARY OF THE INVENTION

The present invention relates to a single phase, non-insulated,miniaturized DC/AC power inverter having an output power density higherthan 3000 W/dm³ and comprising:

-   -   a DC input;    -   an AC output;    -   at least a H full-bridge topology switching circuit having an        input connected to the DC input and an output connected to the        AC output, and comprising switches made of wide-band        semiconductors and preferably of gallium nitride or GaN        semiconductors;    -   at least one common mode noise EMI filter connected between the        DC input and the input of the H full-bridge switching circuit,        between the output of the H full-bridge switching circuit and        the AC output respectively, said common mode noise filters being        referenced to an earth shielding or directly to earth, said        common noise filters comprising filtering inductors and        so-called Y capacitors;    -   at least one differential mode noise EMI filter connected, in        series with a corresponding common mode noise filter, between        the DC input and the input of the H full-bridge switching        circuit, between the output of the H full-bridge switching        circuit and the AC output respectively, said differential mode        noise filters comprising so-called X filtering capacitors and        optionally inductors;    -   a ripple-compensating active filter comprising a switching        half-bridge topology provided in parallel with the H full-bridge        switching circuit and connected to a LC filter, made of at least        one inductor (L6) and a plurality of storage capacitors (C5);        wherein said power inverter is packaged in a casing made of an        external electrically conductive enclosure containing a fan        blowing in an axial direction to a side face of the casing and,        in a stacked elevation arrangement, successively from a bottom        side to a top side, a layer of active filter capacitors, a        heatsink, a layer of wideband semiconductors switches connected        to a PCB with thermal vias and a layer of active filtering        inductors, the fan and the component stacked arrangement being        designed so as, in operation, the external temperature of the        casing does not overcome 60° C. in any point, for an ambient        temperature of maximum 30° C. under a maximum load of 2 kVA.

According to preferred embodiments, the DC/AC power inverter of theinvention also comprises at least one of the following characteristics,or a suitable combination thereof:

-   -   the layer of active filter capacitors is composed of PCB-mounted        rows of regularly spaced multilayer ceramic capacitors (MLCC),        said capacitors being separated by a gap, said gap being        preferably of about 1 mm and oriented in the blowing direction        of the fan;    -   the heatsink is a one-piece machined metallic heatsink selected        from the group consisting of a multiple blades, honeycomb,        interlaced-fins and metal foam heatsink, said heatsink being        adjacent to the layer of active filter capacitors;    -   the casing external conductive enclosure surrounds a conductive        shielding separated thereof by a thermally conductive interface        made of a gap pad;    -   the active filtering inductors are composed of ferrite cores on        which Litz wire is directly wound without a coil former, each        inductor being made of two coils separated by a ceramic foil        placed between the ferrites in order to create an air gap as        well as thermal drain;    -   the layer of wideband semiconductors switches connected to a PCB        with thermal vias is adjacent the heatsink thanks to a ceramic        insulation and microspring contacts, silicone foam being        provided in gaps in order to uniformly spread switch contact        pressure on the heatsink;    -   the casing enclosure, the conductive shielding and the heatsink        are made of copper;    -   the passive filters, i.e. the common mode and differential mode        EMI filters, are separated from the rest in the casing;    -   part of the active filtering inductors are thermally fastened to        the conductive shield.

SHORT DESCRIPTION OF THE DRAWINGS

FIG. 1, already mentioned above, shows an example of designing a basicsolution for EMI filtering (common mode and differential filtering) in aDC/AC power converter.

FIG. 2 schematically represents an example of embodiment for an inverteraccording to the present invention, the inverter having a five legs (orhalf-bridges) topology.

FIG. 3 schematically represents a preferred embodiment for GaN driverprotection against common mode EMI high dV/dt according to the presentinvention.

FIG. 4 represents a thermal mapping for an example of invertercomponents implementation in the present invention, according to a planview thereof, wherein the hottest parts are located in the direct airflow.

FIG. 5 represents, in a height cross-section view, a detailed structureof the thermal interfaces in an inverter according to an embodiment ofthe present invention.

FIG. 6 represents several examples of simulated heatsinks suitable to beused in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

According to one embodiment, the inverter according to the presentinvention has to be designed to meet the requirements of Table 1.

Accordingly, GaN transistors operated in so-called soft switching modeor ZVS (Zero Voltage Switching) mode, combined with a specific parallelactive filtering topology and with the use of multilayer ceramiccapacitors (MLCC) as storage components are the key factors that havecontributed to reaching such a high power density. The shape of theheatsink, the geometric arrangement of the ceramic capacitors and athermal interfaces optimization contribute still to a low temperature ofthe device while in full load operation. An optimized software runningon a fast microcontroller associated with a dedicated logic circuit(CPLD for complex programmable logic device) warrants ZVS behaviorthrough the entire operation range and reduces electromagnetic noise.Double shielding and an optimized set of filters allow the inverter tomeet electromagnetic compliance requirements.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The design methodology applied comprises: precise dimensioning withanalytical calculations and finite elements modeling; use of SPICEsimulations for power and control; 3D mechanical modeling; and use ofthermal simulations. This allowed to create an inverter device meetingall the requirements of Table 1 in a single calculation run.

According to a preferred embodiment of the invention, the use of GaNtechnology enables a power density of ˜143 W/in.³ for the 2 kVA inverterdesigned in this project. The dimensions thereof are approximately2.5×1.6×3.5 inches, corresponding to a volume of about 14 inches³ (or0.2 liter).

GaN transistors have many very useful electrical characteristics (lowR_(ds) _(_) _(on), low Q_(gate) and C_(ds), ultra-low Q_(rr)). Theseclearly create technological advantages over currently and routinelyused MOSFET and IGBT devices (both having small size and low productioncosts). Unfortunately, they also have serious drawbacks due to theirvery fast switching characteristics (for example extremely high“dV/dt”): they are noticeably challenging to drive and also requiresensitive electromagnetic noise management. Another pitfall is the highvoltage drop due to the reverse current when the GaN is turned off. Onesolution selected according to the present invention to overcome thesedifficulties consists in controlling all GaN transistors using softswitching (or ZVS switching) through the entire operation range.

In order to combine a continuous current at the 450 V input stage withan alternating 240 V output voltage, an inverter 1 with at least a threelegs topology (full-bridge or 2-legs topology with a supplemental activefilter) is chosen. Preferably, a five legs topology is chosen accordingto a preferred embodiment shown in FIG. 2, because it minimizes energytransfer within the inverter. Accordingly the first half-bridge and thesecond half-bridge are each preferably split by an additionalhalf-bridge mounted thereon in parallel. It allows accommodating highcurrent and slight switching time differences. Two half bridges 201 (HB)generate the line voltage, while two further half bridges 202 generatethe neutral voltage and the last half bridge 203 is used as theabove-mentioned active filter.

According to this preferred embodiment (see further FIG. 2), inductorsL1 to L6 are rated between 10 μH and 50 μH. Due to the active filter 203(with C5/L6), input capacitor C1 is reduced to less than 15 μF and C5 israted at less than 150 μF. Common mode inductors (L7 to L16, seeinversed “C” symbol) are rated between 200 μH and 1 mH. The total ratingof corresponding Y capacitors (C7, C8, C10-C17, C21, C22) is more than500 nF while keeping the leakage current below the allowed value(initially 5 mA) because the output sine wave is symmetric between L+and L−, i.e. (V_(L)+V_(N))/2˜=(V_(L+)+V_(L−))/2˜=V_(Earth) with splitphase grounding configuration and cancels the leakage current, andbecause some Y capacitors (C7, C8) return to the shield. The EMCdifferential inductors (L17 to L22, see “Z” symbol) are rated between 10μH and 20 μH and the X capacitors (C2, C6, C9, C18 to C20) range from 1μF to 5 μF.

The high density and the high efficiency of this inverter both come fromoptimized control of the five legs, via switching. For any type of load,this control shall achieve soft switching operation of all GaN deviceswhile minimizing reverse currents during the dead times. A controlalgorithm ensures that the module is naturally protected againstovercurrents. During the debug phase, problems were encountered by theinventors, due to the high processing load demanded by the controlalgorithm. Finally the processor was upgraded, by use of a 40% fasterpin-to-pin compatible model.

The objectives of the control are achieved by applying the followingprinciples:

-   -   digital control based on a fast microcontroller combined with a        dedicated logical circuit (CPLD);    -   fast measurement of input/output currents and voltages;    -   efficient feedback on the switching events of the HBs;    -   a learning algorithm for driving the active filter;    -   optimization of the switching frequency between 35 and 240 kHz        depending on the output current; a variable phase shift between        the HBs (0° or 90°) and a dead time modulation of the five HBs        (50 ns to 3 μs). The switching losses are then almost canceled        and the frequency increase helps to optimize (reduce) the size        of the passive components.

Practicing phase shift between the neutral and the line HBs (2 or 4resp.) is necessary because the DMN filtering inductors are optimized atno phase shift. Soft switching does thus not occur anymore at each GaNswitch. Moreover as switching is effected at extremely high speed, andwith some uncertainty upon the current flowing in the DMN filteringinductors, next current switch may occur at a current value that has not(yet) returned to zero, thus leading to “not being ZVS”. A solutionfound for letting the current go closer to zero is to increase the deadtime of the switch (not shown).

Due to the high speed switching in the converter of the presentinvention, according to one embodiment, no direct current measurement iscarried out but capacitive voltage divider 301 (C33, C34), is used fordetecting when the current goes to zero (see FIG. 3). By suitable choiceof the capacitors, this capacitive divider allows the processor tomanage an acceptable voltage measurement (typically about 5 V instead ofmaximum peak voltage of 450 V).

In this invention the robustness of the GaN control is critical. Indeed,GaNs switch extremely fast so that they generate high “dV/dt” across thecontrol isolation, far beyond the allowed values for most of the driverscurrently on the market. Furthermore, the gate voltage threshold is verylow. Still according to the invention, a very compact, low cost andextremely robust driver circuitry has been designed that can drive GaNtransistors well within their specifications (see FIG. 3). According toone embodiment shown on FIG. 3, one takes advantage of additional sourceand gate inductances (L31, L32) to reject CMN traveling in the GaNsdirectly to ground, without affecting GaN driver 303. CMN filter 302 isprovided therefor (L31, C31, L32, C32).

Selecting a right GaN package is also very important. According to anembodiment, a SMD (surface mount) model with a 2-source access, one forthe power, one for the command, was selected as the best choice for thisdesign. It allows safe control of the transistor. Moreover, a smallpackage reduces the parasitic inductances and consequently thefunctional overvoltage. The PCB layout and the positioning of thedecoupling capacitors are crucial for operating the GaN properly.

120 Hz Input Current/Voltage Ripple Requirement

To meet the ripple requirement on DC voltage/current input a parallelactive filter was designed that can compensate ripple more efficientlythan using a large capacitor at the input side. The adopted solution isalso more reliable than the use of a “boost”-based topology for whichthe working voltages could rise up to the limit V_(max) of the GaNtransistors.

The active filter works with higher voltage variations (˜200 V_(pk-pk))and stores the corresponding energy in ceramic capacitors whosecapacitance rises as the voltage decreases, leading to three benefits:

-   -   size reduction of the input tank capacitor C1 (less than 15 μF),    -   size reduction of the filter capacitor C5 to less than 150 μF,    -   inverter robustness due to the use of the GaNs below 450 V_(dc).

The software also contributes thereto; the algorithm maintains V_(in)constant while allowing a larger ripple across the active filter.Moreover, a learning algorithm still reduces the input ripple (by afactor of 3) through correction of the modeling errors due to thepresence of dead times.

Miniaturization of Components for DC-AC Conversion

According to an embodiment, use of MLCC capacitors (i.e. ceramiccapacitors) for energy storage leads to a more compact and efficientmodule.

Moreover magnetic components are mainly composed of ferrite whosemagnetic losses are known to be very low at high frequencies. The use ofLitz wires minimizes the losses due to skin and proximity effects. Forfurther miniaturization, the wires are wound directly onto the ferrite,without a coil former. Their cooling is provided by the air flow of thefan and by use of an aluminum oxide foil placed in the middle of theferrite to create the requested air gap plus a thermal drain. The sizeof the filter capacitors and inductors is optimized by increasingallowed ripple current.

As to the output current, an open loop Hall sensor combined with anelectromagnetic shield leads to a very compact measurement device,offering galvanic decoupling and reducing the sensitivity to common modeand parasitic inductance noise. Time response thereof is very shortwhich contributes to protect the inverter from short-circuit or highload impacts.

It is wise to note that all other current estimations (I_(inductor),etc.) are made by state observers without current sensors (sensorlessmeasures, e. g. voltages), thereby reducing the overall inverter size.

Thanks to a specific GaN control modulation which reduces the currentwithin the filter inductors L7-L8 (see FIG. 2), their core size isreduced without reaching saturation level.

Obtaining a sandwich structure for all the PCB boards and the heatsinkrepresents a real challenge. As shown on FIG. 5, it was obtained byusing micro-spring contacts 507, custom heatsink 512 made by EDM(Electrical Discharge Machining), ultra-thin PCB boards 510, 513, etc.(0.012 inch thick), silicone foam 508 to spread GaN contact pressure onthe heatsink 512. All these technical features greatly helped to reducethe size of the inverter.

According to one embodiment, the inverter module comprises mainly twoparts. The first one includes device control, auxiliary supply, the fivelegs (or half bridges) and their corresponding drivers together with theheatsink.

The second part includes the passive filters.

Preferably, a soft switching LLC resonant topology is used for theisolated auxiliary supply 12V/5V/3.3V (˜10 W). This reduces the volumethereof to less than 0.128 in.³ (0.8×0.8×0.2 in.), which enablessuitable integration within the above-mentioned control part on anunique PCB.

Thermal Management

Based on the estimated and simulated losses, forced-air cooling is theonly viable solution able to sufficiently reduce the thermal resistanceto ambient air. According to an embodiment, an efficient axial fan(˜1.57×1.57×0.6 in.) is placed in the middle of the front plate.

The thermal simulation mapping in FIG. 4 shows the result when allcomponents are optimally positioned around the fan, namely:

-   -   hottest components placed in the direct air flow;    -   exchange surface areas maximized;    -   pressure losses minimized;    -   air speed near the side optimized and    -   fresh air entry near the GaN heatsink to minimize the thermal        resistance, maximizing the inverter efficiency.

Choosing suitable thermal interfaces is then very critical in reducinghot spots on the outer inverter surface. FIG. 5 shows the thermal stackor sandwich according to one embodiment (height cross-section view). TheGaN junction temperature does not exceed 60° C. with an ambienttemperature of 30° C. at 2 kW load.

FIG. 5 shows a detailed structure of the thermal interfaces according toone embodiment. For one GaN transistor 509 (˜2 W loss), the thermalimpedances are as follows:

-   -   GaN junction thermal pad: 0.5° C./W;    -   PCB design 510 maximizing heat transfer from the GaN transistor        509 to the heatsink 512: 1.1° C./W;    -   thermal compound with aluminum oxide dust: 0.3° C./W;    -   ceramic insulation foil with aluminum nitride 511: 0.02° C./W;    -   thermally conductive glue with silver dust: 0.15° C./W and    -   honeycomb-shaped heatsink 512 with forced air (see below): 13°        C./W (relative to a single GaN).

The external shield 501, 503 and the heatsink 512 are both made ofcopper, while the storage capacitors 514 are ceramic MLCC. Bothmaterials were chosen to enhance heat flux and exchange surface area.The capacitor assembly constituting the active filter is an energystorage device but is also an extension of the heatsink 512. The airflow between each MLCC row (preferably with a gap of ±0.04 in. or 1 mmbetween capacitors) enhances the cooling effect, as the capacitors sidesplay the role of fins. The volume occupied by the energy storage unitacts as a second heatsink, due to the assembly geometry and thecapacitor type (good thermal conductor).

Several types of heatsinks as shown in FIG. 6 have been thermallysimulated and compared with the above-mentioned 3D model (multipleblades 601, honeycomb 602, fins interlaced 603 or not, copper foam 604,etc.).

Preferably a honeycomb heatsink 602 has been selected (Rth_total=1.3°C./W (10 GaN); L2.79×W0.83×H0.26 in.) because it minimizes GaNtemperature and has holes large enough to avoid any clogging by dust.The two-dimensional structure surfacically distributes the temperatureand further reduces the number of hot spots.

Several inductors 504 (but not all) are preferably thermally fastened tothe copper shield 503. In order to meet the external enclosure 60° C.temperature limit requirement, a Gap-Pad 502 provides an electricallyinsulating but thermally conductive interface between the shield 503 andthe external copper enclosure 501. Thereby the thermal resistance of theinterface helps to extract heat from the hottest inner components andprevent this heat to be dissipated locally by the external enclosure.

Electromagnetic Compliance (EMC)

In order to be compliant with FCC part 15 class B (for residentialequipment, which is more restrictive than FCC Class A, for commercial orindustrial equipment), the choice of the topology design and of themodulation type has been based on noise source models. Each filter hasbeen simulated with an established noise model to optimize the inductordesign and the PCB routing. Key factors according to the presentinvention to meet for class B can be summarized as follows:

-   -   soft switching operation of the main switches and auxiliary        supply independently of the load;    -   variable frequency and specific spread spectrum modulation;    -   a first internal shield electrically connected to (L−=O V DC);    -   a second shield (external enclosure) and a last filter stage        shielding;    -   an AC_(out) filter referenced to (L−);    -   the use of several small filters instead of a large one;    -   the suppression of all the resonant poles at frequencies higher        than 50 kHz;    -   the use of ceramic capacitors to minimize the parasitic        inductances and their size;    -   the minimization of coupling between filters;    -   the minimization of capacitive coupling in the inductor design.

LIST OF REFERENCE SYMBOLS

-   -   100 Common mode noise filter    -   101 Differential mode noise filter    -   201 Line switch half bridge    -   202 Neutral switch half bridge    -   203 Active filter half bridge    -   204 Earth shielding or connection    -   301 Capacitive divider for zero-current crossing detection    -   302 CMN filter for GaN switch gate    -   303 GaN driver    -   501 Copper enclosure    -   502 Insulation/thermal interface    -   503 Copper shielding    -   504 Inductor(s)    -   505 Ceramic inductor gap    -   506 PCB interconnection    -   507 Micro-spring contacts    -   508 Silicone foam    -   509 GaN switch    -   510 PCB with thermal vias    -   511 Ceramic insulation    -   512 Honeycomb heatsink    -   513 PCB for mounting storage capacitors    -   514 Active filter ceramic capacitor    -   601 Multiple blades heatsink    -   602 Honeycomb heatsink    -   603 Interlaced fins heatsink    -   604 Copper foam heatsink

TABLE 1 Parameter Requirement Comment Maximum load 2 kVA At 240 V RMS ACat 60 Hz Power density >50 W/in³ Volume <40 in³(0.66 I) Rectangularenclosure, max. dim. 20 in., min. 0.5 in. Voltage input 450 V DC, R = 10Ω Voltage output 240 +/− 12 V AC Single phase Frequency output 60 +/−0.3 Hz  Single phase Power factor 0.7-1 Leading or lagging of load THD +N of Vout <5% Total harmonic distorsion + noise THD + N of Iout <5%Total harmonic distorsion + noise Efficiency >95%  Measured by weightedaverage at different loads (var. of CEC method) Input ripple <20% Measured as I_(pp)/I_(av) from current (120 Hz) 450 V supply in serieswith a 10 Ω resistor Input ripple <3% Measured as V_(pp)/V_(av) fromvoltage (120 Hz) 450 V supply in series with a 10 Ω resistor Maximumouter <60° C. Tested at 15-30° C. ambient temperature (any outside pointto be touched <60° C.) Electromagnetic FCC Part 15 B compliance Max.current on <5 mA chassis GND connex.

The invention claimed is:
 1. A single phase, non-insulated, miniaturizedDC/AC power inverter (1) having an output power density higher than 3000W/dm³ and comprising: a DC input; an AC output; at least a H full-bridgetopology switching circuit (201, 202) having an input connected to theDC input and an output connected to the AC output, and comprisingswitches made of wide-band semiconductors and preferably of galliumnitride or GaN semiconductors; at least one common mode noiseElectromagnetic Interference (EMI) filter (100) connected between the DCinput and the input of the H full-bridge switching circuit, between theoutput of the H full-bridge switching circuit and the AC outputrespectively, said common mode noise filters (100) being referenced toan earth shielding or directly to earth (204), said common noise filters(100) comprising filtering inductors and so-called Y capacitors; atleast one differential mode noise Electromagnetic Interference (EMI)filter (101) connected, in series with a corresponding common mode noisefilter (100), between the DC input and the input of the H full-bridgeswitching circuit, between the output of the H full-bridge switchingcircuit and the AC output respectively, said differential mode noisefilters (101) comprising so-called X filtering capacitors and optionallyinductors; a ripple-compensating active filter comprising a switchinghalf-bridge topology (203) provided in parallel with the H full-bridgeswitching circuit and connected to a LC filter, made of at least oneinductor (L6) and at least one storage capacitor (C5); wherein saidpower inverter (1) is packaged in a casing made of an externalelectrically conductive enclosure (501) containing a fan blowing in anaxial direction to a side face of the casing and, in a stacked elevationarrangement, successively from a bottom side to a top side, a layer ofactive filter capacitors (514), a heatsink (512), a layer of widebandsemiconductors switches (509) connected to a Printed Circuit Board (PCB)with thermal vias (510) and a layer of active filtering inductors (504),the fan and the component stacked arrangement being designed so as, inoperation, an external temperature of the casing does not overcome 60°C. in any point, for an ambient temperature of maximum 30° C. under amaximum load of 2 kVA.
 2. The DC/AC power inverter of claim 1, whereinthe layer of active filter capacitors (514) is composed of PrintedCircuit Board (PCB) mounted (513) rows of regularly spaced multilayerceramic capacitors (MLCC), said capacitors being separated by a gap,said gap being preferably of about 1 mm and oriented in the blowingdirection of the fan.
 3. The DC/AC power inverter of claim 1, whereinthe heatsink (512) is a one-piece machined metallic heatsink selectedfrom the group consisting of a multiple blades, honeycomb,interlaced-fins and metal foam heatsink, said heatsink (512) beingadjacent to the layer of active filter capacitors (514).
 4. The DC/ACpower inverter of claim 1, wherein the casing external conductiveenclosure (501) surrounds a conductive shielding (503) separated thereofby a thermally conductive interface made of a gap pad (502).
 5. TheDC/AC power inverter of claim 1, wherein the active filtering inductors(504) are composed of ferrite cores on which Litz wire is directly woundwithout a coil former, each inductor (504) being made of two coilsseparated by a ceramic foil (505) placed between the ferrites cores inorder to create an air gap as well as thermal drain.
 6. The DC/AC powerinverter of claim 1, wherein the layer of wideband semiconductorsswitches (509) connected to a PCB with thermal vias (510) is adjacentthe heatsink thanks to a ceramic insulation (511) and microspringcontacts (507), silicone foam (508) being provided in gaps in order touniformly spread switch contact pressure on the heatsink (512).
 7. TheDC/AC power inverter of claim 4, wherein the casing enclosure (501), theconductive shielding (503) and the heatsink (512) are made of copper. 8.The DC/AC power inverter of claim 1, wherein the common mode anddifferential mode Electromagnetic Interference (EMI) filters, areseparated from the rest in the casing.
 9. The DC/AC power inverter ofclaim 1, wherein part of the active filtering inductors (504) arethermally fastened to a conductive shield (503).